DOPAMINE JAHANGIR AHMAD

HISTORYThe function of dopamine as a neurotransmitter was discovered in 1958 by ArvidCarlssonand Nils-ÅkeHillarpat the Laboratory for Chemical Pharmacology of the National Heart Institute of Sweden. It was named dopamine because it was a monoamine, and its synthetic precursor was 3,4-dihydroxyphenylalanine . ArvidCarlssonwas awarded the 2000 Nobel prize for physiology or medicine for showing that dopamine is not just a precursor of norepinephrine (noradrenaline) and epinephrine (adrenaline) but a neurotransmitter, as well.

INTRODUCTIONDopamine is an endogenous catecholamine that serve as both a neurotransmitter and a precursor of nor epinephrine synthesis.When given as an exogenous drug dopamine activates a variety of receptors in dose dependent manner.Regulates cardiac, vascular and endocrine function.

Each ampoule contains 200 mg /5ml

STRUCTURE

SYNTHESIS

RECEPTORS Dopamine acts through D1 , D2 as well as adrenergic alpha and B1 receptors ( But not B2)D1 and D2 receptors are the most abundant and widespread in areas receiving a dopaminergic innervation ( namely the striatum ,limbic system, thalamus and hypothalamus) as are D2 receptors, which also occur in the pituitry gland

Dopamine acts through D1 , D2 as well as adrenergic alpha and B1 receptors ( But not B2)

D1 and D2 receptors are the most abundant and widespread in areas receiving a dopaminergic innervation ( namely the striatum ,limbic system, thalamus and hypothalamus) as are D2 receptors, which also occur in the pituitry gland

MECHANISM OF ACTIONAt low dose (0.5 to 3 mic /kg /min ):- Selectively activates dopamine specific receptors in the renal and splanchnic circulation. Increase blood flow in these region. Low dose dopamine also directly affects renal tubular epithelial cells. It causes an increase in urinary Na excretion

At low dose (0.5 to 3 mic /kg /min ):-

Contd….Intermediate dose(3 to 10 mic /kg /min ):-It stimulates B1 receptors in the heart and peripheral circulation. Increases myocardial contractility, increases heart rate and peripheral vasodilatation It increases myocardial oxygen demand, so when ever dopamine is to be used oxygen must be supplemented Over all increase in cardiac output Contractile response to dopamine is modest when compared to dobutamine

Intermediate dose(3 to 10 mic /kg /min ):-

Contd…At high dose (> 10 mic /kg / min ):- Dopamine produces a progressive activation of alpha receptors in the systemic and pulmonary circulation resulting in progressive pulmonary and systemic vasoconstriction This vassopressor effect by virtue of increasing ventricular afterload

At high dose (> 10 mic /kg / min ):-

Contd.. Dopamine not effective orally and does not cross blood brain barrier in sufficient amounts to cause CNS effects.

PHARMACOKINETICSRapid metabolism of dopamine mandates its use as a continuous infusion. A portion of the positive inotropic effect of dopamine is due to stimulation of release of endogenous norpinephrine which may predispose to development of cardiac disarrythmias never theless, dopamine is less disarrythmogenic than epinephrine It is used only intravenously .

CLINICAL USESDopamine is often used in situation where both cardiac stimulation and peripheral vasoconstriction desired such ascardiogenic shockAlso used to correct the hypotension in the septic shock .But norepinephrine become the preferred vassopressor in this conditionLow dose is often used in an attempt to prevent or reverse acute renal failure

Contd…Drug initially administered at a rate of 2 to 5 mic / kg /min . During infusion ,pt require clinical assessments of myocardial function perfusion of vitals organs such as the brain , and the production of urineMost pts should receive intensive care with monitoring of arterial and venous pressures and ECGReduction in urine flow ,tachycardia or the development of arrhythmias may be indications to slow or terminate the infusion

DOPAMINE IN PULMONARY OEDEMAThe sympathomimetic amines dopamine is potent ionotropic agentsUsed in pulmonary edemaForcefully contracts the heart and thus decreases the pulmonary load

DOPAMINE INFUSION IN WHICH FLUID ?D-5-- NoRL -- NoNS -- yes DNS-- NoHEMACCIL -- No

DOPAMINE AND ADRENALINE/NORADRENALINE COMBINED INFUSION

DOPAMINE AND DOBUTAMINE COMBINED INFUSIONThe divergent pharmacologic effects of dopamine and dobutamine make their use in combination potentially useful.Infusion of the combination of dopamine and dobutamine have been noted to produce a greater improvement in cardiac output, at lower doses, than can be achieved by either drug alone.

Conti-Low dose simultaneously increases: Glomerular filtration rate Renal blood flow Urine output

DOSE AND ADMINISTRATIONCommercial preparation of dopamine are concentrated drug solution [Containing 40 mg /80 mg dopamine HCL /ml]Provided in small volume vial / ampoule in 5 ml /10 mlTHE Preparation must be diluted to prevent intense vasoconstriction during drug infusionDopamine solution diluted 100-fold in isotonic saline to prepare the infusateAlways delivered into , large central veins

DOSING REGIMENWeight basedThere are two recommended doses:- 3 to 10 mic /kg /min is for augmenting cardiac output thereby increasing BP More than 10 mic /kg /min is recommended to increase the blood pressure directly

3 to 10 mic /kg /min is for augmenting cardiac output thereby increasing BP

More than 10 mic /kg /min is recommended to increase the blood pressure directly

INCOMPABILITIESLike dobutamine, dopamine is inactivated by higher PH So ,alkaline fluids should not be infused along with dopamineINFUSATE:- Use 5 ml 2 vials containing 40 mg /ml dopamine HCL add to 500 ml isotonic saline [Final concentration= 40mic /drop ]

Use 5 ml 2 vials containing 40 mg /ml dopamine HCL add to 500 ml isotonic saline [Final concentration= 40mic /drop ]

PRECAUTIONSBefore dopamine is administered to pt in shock ,hypovolemia should be corrected by transfusion of whole blood , plasma or other appropriate fluid

ADVERSE EFFECTSTachyarrhythmia's are the most common adverse effects of dopamineMalignant tachyarrhythmia [ Multifocal ventricular ectopic , ventricular tachycardia ]The most feared complication of dopamine infusion is limb necrosisExtravasations of drug through a peripheral vein can be treated with local injection of phentolamine [5 to 10 mg in 15 ml saline ]

Tachyarrhythmia's are the most common adverse effects of dopamine

Malignant tachyarrhythmia [ Multifocal ventricular ectopic , ventricular tachycardia ]

The most feared complication of dopamine infusion is limb necrosis

Extravasations of drug through a peripheral vein can be treated with local injection of phentolamine [5 to 10 mg in 15 ml saline ]

Contd…Allergic reactions Delays gastric emptying which could predispose to nosocomial pneumoniaIf pt is on dopamine infusion and is to be anaesthetized , he / she will be treated as a full stomach pt Less dysarrytmogenic than epinephrine

Contd…Continuous infusion of dopamine increase intraocular pressureVentilation effects :- Infusion of dopamine interferes with the ventilatory response to arterial hypoxemia They results in unexpected depression of ventilation ABG have been observed to deteriote during infusion of dopamine

Contd…Hyperglycemia that is commonly present in pts receiving a continuous infusion of dopamine is likely to reflect drug induced inhibition of insulin secretion

DRUGS MAY INTERACTS WITH DOPAMINECyclopropaneBromocriptineDyhydroergotamineEntacaponeHalothaneLinezolidePhenytoine

CONTRAINDICATIONPt receiving MAO inhibitorsTricyclic antidepressants agentsPheochromocytomaUncorrected tachyarrhythmiaVentricular fibrillation

If dopamine liquid falls on floor /cloth it gives permanent staining if allowed to dry and was not mopped off wet

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